1. Field of the Invention
This invention relates to relays and more particularly to a method and apparatus for adjusting the contact system of such a relay.
2. Prior Art
This invention is directed to that type of electromagnetic relay which has a switching element which is mounted at one end and which is elastic or resilient such that its free end can move to cooperate with at least one other switching member to effectuate a contact. Such a switching element can, for example, be a contact tongue, an arm, an armature, a contact spring or an armature contact or any other known variant. In addition the invention is directed to a method of adjusting such a relay.
Most electromagnetic relays have an operating air gap. In such relays adjustment of the air gap is provided either in the magnetic circuit or in the contact spacing between the contact providing parts during the production of the relay. This adjustment is required in order to avoid large variations in the operating values of the relays. Such an adjustment has been known to be provided by means of adjusting screws or by means of controlled bending of the sheet metal parts with the aid of adjusting clamps. Such adjustment operations require painstaking care and manual dexterity and cannot generally be automated . During the course of miniaturizing such relays, the adjusting problem has been aggravated due to the fact that, frequently, the parts to be adjusted are often accessible to the adjusting tools only with great difficulty. Further in conventional miniature sealed relays wherein the contact system is internally sealed, adjustment after assembly can be virtually impossible particularly where it is required that adjustment tools be given access to the components to be adjusted.
An adjustable miniature relay is illustrated in U.S. Pat. No. 3,477,045. In such a type of relay, subsequent adjustment is thought to be provided for by means of an adjustment spring device in cooperation with screws in the casing wall. However such a device does not provide a complete solution to the problem since the adjusting mechanism is not only very expensive but is no longer functionable after completion of the final sealing of the adjustment member.
It has also been suggested, in connection with contact relays having a ferromagnetic switching tongue received in a glass casing, to subsequently deform the tongue by means of a magnetic field applied from the exterior. See for example U.S. Pat. No. 3,242,557. However the bending of a spring tongue which abuts an opposing contact requires an extremely high magnetic force. Thus, desired adjustment cannot be readily obtained. Further the contact force cannot be adjusted independently from the contact spacing and an initial grid potential vis-a-vis opposed rigid contacts cannot be obtained with this known method.